In the core kernel, an srcu_struct structure created by DEFINE_SRCU() or friends lives as long as the kernel does, so there are no particular requirements surrounding the end of that structure's life. In contrast, when DEFINE_SRCU() and friends are used within a module, the corresponding srcu_struct structures' lifetimes end when that module exits. This in turn means that if such a structure was passed to call_srcu(), then srcu_barrier() must be invoked after the last call_srcu() invocation but before the module exits.
This commit therefore adds a comment stating this. Reported-by: Alexander Aring <[email protected]> Signed-off-by: Paul E. McKenney <[email protected]> --- include/linux/srcutree.h | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index ad9d9658b0a2..93b76e543894 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -214,6 +214,12 @@ struct srcu_struct { * instead of smp_mb(), and given that the first (for example) * srcu_read_lock_fast() might race with the first synchronize_srcu(), * this different must be specified at initialization time. + * + * If you use any of the DEFINE_SRCU() functions within a module, the + * module-entry code will invoke init_srcu_struct() and the module-exit + * code will invoke cleanup_srcu_struct(). This means that if your module + * passes the resulting srcu_struct structure to call_srcu(), you will + * need to also pass this structure to srcu_barrier() prior to module exit. */ #ifdef MODULE # define __DEFINE_SRCU(name, fast, is_static) \ -- 2.40.1
